Refrigeration apparatus with means to increase liquid refrigerant pressure



Sept. 22, 1970 T, CHAMBERS 3,529,433

REFRIGERATION APPARATUS H MEANS TO INCREASE v LIQUID REFRIGER PRESSURE E 7 Filed March 17, 1969 2 Sheets-Sheet l J .//;;z 7 J /7 INVENT R.

Sept. 22, 1970 1', CHAMBE 3,529,433 REFRIGERATIO PPARATUS a ANS TO INCREASE LIQUID REFRIGER PRESSURE Filed March 17, 1969 2 Sheets-Sheet 2 50 v I 'INVENTOR.

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United States Patent REFRIGERATION APPARATUS WITH MEANS TO INCREASE LIQUID REFRIGERANT PRESSURE Dale '1. Chambers, Dayton, Ohio, assignor to Chrysler Corporation, Highland Park, Mich., a corporation of Delaware Filed Mar. 17, 1969, Ser. No. 807,693 Int. Cl. F25!) 41/00 U.S. Cl. 62-196 7 Claims ABSTRACT OF THE DISCLOSURE Refrigeration apparatus including a compressor, air cooled condenser, reservoir, control valve, expansion device, and cooler connected in series. The reservoir is heated in response toa low pressure condition existing in a line between a check valve and the reservoir. A bypass is provided to permit liquid refrigerant to bypass the expansion device on start-up of the apparatus.

BACKGROUND OF THE INVENTION This invention relates to refrigeration apparatus, and more particularly, to water chiller refrigeration apparatus.

Water chiller refrigeration apparatus includes a closed refrigerant circuit having a compressor, a condenser, an expansion valve, and a cooler connected by refrigerant lines. In many water chiller systems, the condensers are air cooled, i.e., the refrigerant in the condensers is condensed by the ambient conditions surrounding the condenser which is placed on the exterior of the building.

While refrigeration systems have historically been used primarily during periods of warm weather, it has recently become more common to utilize refrigeration systems even when the ambient temperature is relatively low.

During periods of cold weather, after the chiller system has been shut down for a period of time, the pressure of refrigerant in a conventional system drops to a relatively low value. In such case, the pressure in the condenser and receiver, if one is provided, may be insuificient to cause liquid refrigerant to flow to the evaporator, i.e., the expansion valve may remain closed. This makes it impossible to build up pressure in the cooler and the compressor if it starts, will soon shut down, thus preventing operation of the refrigerant system. The present invention overcomes many of the objections to the prior known systems.

SUMMARY OF THE INVENTION Briefly, this invention comprises means for heating a reservoir of refrigerant when the pressure of the refrigerant falls below a predetermined value, and means for permitting refrigerant to bypass the expansion device during start-up of the apparatus.

One of the primary objects of the present invention is to provide water chiller apparatus adapted to function properly even after long periods in a shut down condition during relatively cold weather.

Another object of this invention is to provide apparatus of the class described which causes the suction temperature to rapidly rise and normalize within a few minutes after start-up.

A further object of this invention is to provide apparatus such as described which permits refrigerant to be bypassed around the expansion valve, and forced into the cooler during initial operating conditions.

Another object of this invention is to provide apparatus of the type described which may be mounted outdoors, releasing valuable interior space from equipment space to occupancy use.

3,529,433 Patented Sept. 22, 1970 Still another object of the present invention is to provide apparatus such as described which is economical in construction and efiicient in operation.

Other objects and features of this invention will be made apparent as the description progresses.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings, in which one of various possible embodiments is illustrated, I FIG. 1 is a perspective view of the apparatus of this 1nvent10n;

FIG. 2 is a schematic view of the apparatus when the same is in a shutdown condition;

FIG. 3 is a schematic view of the apparatus when the same is in a starting condition during cold weather;

FIG. 4 is a schematic view of the apparatus when the same is in a running oroperating condition during cold weather; and

FIG. 5 is a graph of suction temperature during the first few minutes of operation of the apparatus of this invention at zero degrees Fahrenheit ambient temperature.

Like parts are indicated by corresponding reference characters throughout the several views of the drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, the refrigeration apparatus of this invention is shown generally to include a compressor 1, an air cooled condenser 3, a reservoir or storage unit 5, a control valve 7, an expansion device or valve 9, a bypass arrangement 11 and a cooler 13 connected together in a closed refrigerant system by lines 15, 17, 19, 21 and 23. In addition, the system may include a conventional receiver 25, if desired, and a subcooling coil 27 (FIG. 1) as is conventional in many systems of this type. As is known, a subcooling coil, when the refrigerant system is operating, slightly increases refrigeration capacity, but is primarily useful in the prevention of flashing of refrigerant ahead of the expansion device. The condenser 3 has dampers 28 which are operated in a known manner as a function of liquid refrigerant pressure to control head pressure. When the liquid pressure drops with decreasing outdoor temperature, the dampers close and reduce air flow through the condenser. If the system has been shut down for a period of time in cold weather, the dampers will be in a closed position as indicated in FIG. 2. While dampers are shown herein, other known means of head pressure control may be utilized.

A check valve 29 is located in line 17 ahead of the inlet to reservoir 5. Check valve 29 will remain open as long as the pressure of refrigerant in line 17 upstream of the valve is equal to or greater than the pressure within reservoir 5.

A heater in the form of a heating wire or coil 31 is Wrapped around the reservoir 5 to heat the refrigerant within the latter in response to a signal. The signal is provided through means of a pressure sensor 33 located in line 17 downstream of check valve 29 and upstream of the inlet to reservoir 5. The pressure sensor 33 is adapted to initiate energization of the heater 31 when the pressure in line 17 adjacent the sensor drops below a predetermined value such as p.s.i., for example. The heater will remain energized and heat the liquid refrigerant in reservoir 5, line 19 and line 17 downstream of check valve 29 until the pressure of the liquid refrigerant is raised to some predetermined value, such as 200 p.s.i. for example. If the refrigerant pressure upstream of check valve 29 is lower than the pressure of refrigerant downstream of the check valve, the check valve will 3 remain closed and prevent the passage of refrigerant back toward the condenser 3.

The main solenoid valve 7 is responsive to the environmental control (not shown) and remains closed unless the environmental control is actuated to energize the refrigeration system. It will be understood that unless valve 7 is opened, no refrigerant will be permitted to pass from the reservoir to the cooler 13.

Expansion valve 9 is adapted to be operated in response to the temperature of the refrigerant on the suction side of the compressor 1 in a conventional manner. Bypass 11, which bypasses expansion valve 9, includes a bypass solenoid valve 35 which is adapted to be controlled by pressure sensor 37 located in line 23. Generally, if the compressor suction pressure is below approximately 55 p.s.i., the pressure sensor 37 will cause valve 35 to open. When the pressure in line 23 reaches approximately 65 p.s.i., the bypass valve 35 will be closed. When the valve 35 is open, refrigerant may bypass expansion valve 9 and be delivered to cooler 13.

Operation of the apparatus, with particular reference to the schematic views of FIGS. 2, 3, and 4, is as follows:

It may be assumed that the ambient temperature is zero degrees Fahrenheit. Normally, without the use of a heater, the refrigerant in a typical refrigeration system would equalize at a relatively low value, such as 24 p.s.i., for example, throughout the system. However, as soon as the pressure in line 17 downstream of check valve 29 drops below approximately 170 p.s.i. the heater will be energized and heat the refrigerant in the reservoir. When the refrigerant reaches about 200 p.s.i. the heater is de-energized. The heater then cycles on and off to maintain the refrigerant in reservoir 5, line 17 downstream of check valve 29 and line 19, upstream of main control valve 7, which is closed, at approximately 170 p.s.i. The remainder of the system may drop to approximately 24 p.s.i.

The valve 7 is closed and a substantial portion of the system refrigerant is trapped in reservoir 5 and line 19 between check valve 29 and valve 7. Since the pressure down stream of the check valve is higher than upstream due to the heater 31, the check valve prevents the ingress of refrigerant into condenser 3.

If the valve 7 is opened and the compressor 1 started, refrigerant in line 19 is permitted to flow to the expansion valve 9 and the bypass valve 35. The temperature and pressure on the suction side of the compressor will be pulled down rapidly.

If the expansion valve and sensing bulb are located outdoors, the expansion valve will remain shut even after the compressor starts due to the ambient conditions. This is because the expansion valve senses the ambient temperature until refrigerant gas flow from the evaporator to the compressor is established. Since the expansion valve remains closed, refrigerant cannot flow therethrough to the cooler 13. However, when the pressure in line 23 drops oif, sensor 37 causes valve 35 to be opened, thereby permitting refrigerant to flow through line 21 back to line 19 around expansion valve 9' (see FIG. 3). The cooler 13 is thus supplied with heated refrigerant and this rapidly reverses the momentary drop in suction temperature. In this regard, the graph shown in FIG. 5 is illustrative of the suction temperature during start-up conditions with the present invention. As with any typical air cooled equipment, the suction temperature is initially pulled down rapidly. However, the present invention causes the suction temperature to rapidly rise and normalize at the end of approximately three minutes. The liquid refrigerant boiling in the cooler provides gas which permits the compressor to build up head pressure for normal operation.

During the three minute period the pressure sensor 37 cycles the valve 35 open and closed as the pressure in line 23 gradually increases from approximately 24 p.s.i. to 65 p.s.i., for example. More particularly, the pressure in line 23 is initially raised from 24 p.s.i. to 65 p.s.i. The sensor 37 then causes valve 35 to close and the pressure in line 23 begins to drop. When it reaches approximately p.s.i. the sensor 37 causes valve 35 to open so that the pressure in line 23 will again rise. Meanwhile, since the compressor is running, some refrigerant is passing through the expansion valve to the cooler and the pressure therein rises. As the pressure in line 23 increases the expansion valve becomes more and more effective, thus permitting some of the refrigerant to flow therethrough. When the bypass valve closes for the last time, the pressure in the line 23 does not drop to 55 p.s.i., i.e., it drops back to something above 55 p.s.i., because the apparatus has been running long enough to permit expansion valve to open sufliciently to control the apparatus. Since the pressure does not drop to 55 p.s.i. on this cycle, the bypass valve will not open. When the bypass arrangement stops cycling, normal running conditions have been achieved. The check valve 29 opens since the pressure upstream and downstream of the check valve equalize. Head pressure is then controlled by the operation of dampers 28 or other known controls.

Valve 35 may contain an orifice sized to allow the proper amount of refrigerant to flow therethrough for the particular compressor utilized in the system. It will be seen that the apparatus of this invention, having a heated reservoir and a bypass system for permitting the flow of heated refrigerant around the expansion valve during initial startup conditions in cold weather, will cause suction pressure to rise rapidly after initial pull down and thus permit the apparatus to function normally. The heater 31 and the control 7 are entirely independent of one another and so operate. While the system is operating normally the heater 31 is tie-energized. Since the discharge temperature of the system when operating after start-up is considerably above 200 p.s.i. (22530O p.s.i. for example) the heater remains de-energized.

It will be understood that the system may or may not include a conventional receiver 25 in addition to reservoir 5, depending upon customer preference.

In view of the foregoing it will be noted that the several objects and other advantages are obtanied.

Although only one embodiment of the invention has been disclosed and described, it is apparent that other embodiments and modifications of the invention are possible.

I claim:

1. Refrigerant apparatus comprising a compressor, an air cooled condenser, a reservoir, a main control valve, an expansion device, a cooler, a plurality of lines connecting said condenser, reservoir, control valves, expansion device and cooler in series in a closed circuit, valve means in the line between said condenser and said reservoir adapted to close when the pressure of refrigerant downstream thereof is greater than the pressure of re frigerant upstream thereof, electric heater means connected to said reservoir and adapted to heat refrigerant therein, heater control means responsive to a condition of the refrigerant downstream of said valve means for controlling the energization of said heater, a bypass line connected at one end to the line between said main control valve and said expansion device and connected at the other end to the line between said expansion device and said cooler, a bypass valve in said bypass line, said valve normally being closed, bypass valve control means responsive to a condition of the refrigerant in the line between said cooler and said compressor for opening and closing said bypass valve, said bypass valve control means being adapted to open said bypass valve when the said condition of refrigerant in the line between said cooler and said compressor is below a predetermined value, said condition of refrigerant in the line between said cooler and said compressor being above said predetermined value when said apparatus is running normally during cold weather, whereby refrigerant heated in said reservoir is adapted to flow around said expansion valve from said reservoir to said cooler when the apparatus is started during cold weather.

2. Refrigeration apparatus as set forth in claim 1 wherein said electric heater comprises an electrical wire wrapped around said reservoir.

3. Refrigeration apparatus as set forth in claim 1 wherein said heater control means responsive to a condition of the refrigerant downstream of said valve means comprises a pressure sensing device adapted to sense the refrigerant pressure in the line between said valve means and said reservoir.

4. Refrigeration apparatus as set forth in claim 3 wherein said electric heater comprises an electrical wire wrapped around said reservoir.

5. Refrigeration apparatus as set forth in claim 1 wherein said bypass valve control means comprises a sensor for sensing the pressure of refrigerant between said cooler and said compressor.

6. Refrigeration apparatus as set forth in claim 5 wherein said electric heater comprises an electrical wire wrapped around said reservoir.

7. Refrigeration apparatus as set forth in claim 6 wherein said heater control means responsive to a condition of the refrigerant downstream of said valve means comprises a pressure sensing device adapted to sense the refrigerant pressure in the line between said valve means and said reservoir.

References Cited UNITED STATES PATENTS 3,082,610 3/1963 Marlo 62-196 3,161,029 12/1964 Macrow 62196 MEYER PERLIN, Primary Examiner US. Cl. X.R. 622l6, 278 

